Outboard test stand

So im not 100% sure where this should be...but this looks like a good spot..
Just as the title says...but how do you test your outboard...I didnt want to mount it on a boat due to different mounting holes...so this is what I came up with....post a pic of your test stand if you have one...

It looks like you will be testing with no load on the engine. If you put a container of water under the prop to simulate a load, it will be blown dry in seconds. A closed container would be better, but the circulation will be a lot different than on a boat. If anyone has any ideas on how to load the prop, i would like to see pictures.

Lohring Miller

Lohring...
I think we all know the real answer to that..
connect the prop shaft to a dyno...and then we can dial in the load amount...we will be able to setup the supercharger and fuel injection as well....everyone has a dyno....right...

Lohring...
Heres a thought about that you said about a load on the prop....
Coming off the prop shaft have it spin a disk with holes in it thats inside a bottle filled with oil....should be enough to create a load right...

My solution for a conventional engine was to cut a hole in the bottom of a 5 gallon bucket for a stuffing tube. I then mounted a conventional prop shaft with a short length of flex cable. I could vary the amount of water in the bucket, but needed the lid on to keep the water in. Vibration made mounting everything difficult so I didn't use it much, especially since I don't run nitro engines any more.

Lohring Miller

Ok...so thats very close to what i was thinking....I was drawing plans for a mason jar with a stuffing tube soldered into the lid...then filled with oil as a fluid...attach a disc to the stuffing tube and screw on the lid to the jar ....make a stand for the jar....and fashion a connection to the drive dog on the outboard to turn the whole setup...

Robert,

I tested my Nelson .45 long stroke FAI engine while it was mounted to the entire modified K & B lower unit. The entire modified lower unit, minus a boat propeller, was mounted to a 1/2" thich aluminum angle which was mounted to a 3/4" thick 4' X 6' sheet of plywood. The 4' X 6' plywood sheet was mounted to a 2' X 4' wood base on wheels. I stood behind the plywood sheet during engine tests because the engine was sitting as it would be mounted on the tunnel hull. Sorry, I don't have any photos of this thing. To load the engine, the flywheel was replaced with a standard, carefully balanced, left hand APC prop. The 10 x 7 prop was cut down to an 8" diameter & it was carefully balanced. I also had a 10 X 6 prop cut to an 8" diameter, but never used it. The cut down 10 X 7 prop would allow the engine to turn 32,000+ RPM. Henry Nelson did not want me to turn the engine any faster, therefore the 10 X 6 prop was never tested. I posted a photo of the props, the balanced prop driver, the washer & the prop shaft sleeve.

Jim Allen

Jim..
What a great idea......I do have a k&b lower that can be "sacrificed" for a project like this...thank you for sharing your idea....

Robert,

The K & B lower unit was completely rebuilt to give the rigid, fully adjustable unit I presently use on my tunnel hull. The rebuild included a hardened brass tube for the cable stuffing box with grease fitting, a propeller shaft housing with no play whatsoever & a rebuild of the entire pivot shaft assembly with grease fitting.

Jim Allen

Jim Allen said:

Robert,

The K & B lower unit was completely rebuilt to give the rigid, fully adjustable unit I presently use on my tunnel hull. The rebuild included a hardened brass tube for the cable stuffing box with grease fitting, a propeller shaft housing with no play whatsoever & a rebuild of the entire pivot shaft assembly with grease fitting.

Jim Allen

Click to expand...

Jim,
Can you make more of those prop shafts? I would love to have a couple for saw 45ob. Are they rebuildable?

Jim Allen said:

Robert,

The K & B lower unit was completely rebuilt to give the rigid, fully adjustable unit I presently use on my tunnel hull. The rebuild included a hardened brass tube for the cable stuffing box with grease fitting, a propeller shaft housing with no play whatsoever & a rebuild of the entire pivot shaft assembly with grease fitting.

Jim Allen

Click to expand...

Jim
How does the boat trim out with very little cavitation plate? I tried that many yrs ago & the boat hopped real bad.

dion smith said:

Jim,
Can you make more of those prop shafts? I would love to have a couple for saw 45ob. Are they rebuildable?

Click to expand...

Dion,

I did not make new prop shafts. I use the stock unhardened steel shafts with a precisely machined B-10 Bearium metal bushing. Notice that the bushing has a shoulder machined on it for the teflon thrust washer to ride against. I also machined a new drive dog. The unit now has shown to have very high wear resistance, which is possibly helped with the stuffing tube grease fitting. The #2 Special Marine Lubriplate Grease travels downward lubricating both the stuffing tube & the propeller shaft.

Jim Allen

Alan Elzer said:

Jim
How does the boat trim out with very little cavitation plate? I tried that many yrs ago & the boat hopped real bad.

Click to expand...

Alan,

I believe there are several things working together to keep this tunnel hull from hopping. The modified mounting bracket allows the prop to set at heights & thrust angles that would not be possible with a stock K & B unit. I also have an adjustable CG system & I use larger diameter (Barr Cut), higher pitch propellers as recommended by John Finch.

Jim Allen

Jim Allen said:

Dion,

I did not make new prop shafts. I use the stock unhardened steel shafts with a precisely machined B-10 Bearium metal bushing. Notice that the bushing has a shoulder machined on it for the teflon thrust washer to ride against. I also machined a new drive dog. The unit now has shown to have very high wear resistance, which is possibly helped with the stuffing tube grease fitting. The #2 Special Marine Lubriplate Grease travels downward lubricating both the stuffing tube & the propeller shaft.

Jim Allen

Click to expand...

Thanks for the reply Jim, I might just rebuild what I have already.